We are regularly contacted (thank you) with specific questions regarding the construction of NiSi products: glass quality, characteristics of Multi Coating, IR, Nano® and so on.
Whilst it is truly a great pleasure to speak with you individually, we have decided to answer some of the most frequently raised questions here.
Third Party Filter Manufacture? Not at NiSi.
Apart from the company that provides the untreated, lens grade optical glass (exclusive to NiSi), our filters are 100% made by NiSi – from coating, shaping and finishing right through to final inspection and packaging. The only way to guarantee NiSi quality is to do everything ourselves. So if it says NiSi on the box, you know it is NiSi through and through.
The Quality of NiSi Glass
Until quite recently, photographic filters were made almost entirely in resin. Even early cinematic glass filters were a resin layer sandwiched in glass. As technology has advanced, some manufacturers preferred to continue to focus less on optical quality and more on the ease and relatively low production cost of resin.
This compromise is absolutely out of place nowadays, especially when filters are being placed in front of lenses worth hundreds or even thousands of pounds, mounted on equally expensive cameras.
Unfortunately the problem of quality vs cost of production can persist with glass. Even well-made glass like the B270 Optical Glass, used by some British manufacturers, does not allow you to achieve the same excellent properties as the glass of photographic lenses. Although imperceptible at first glance, the shots lose definition. And it’s not just about definition, it’s about chromatic aberrations, resistance to flare, ghosting (refraction caused by dual layer filters) and so on. For the above reasons, the well-known lens manufacturer Zeiss has always stated that it does not recommend the use of filters in front of its lenses. “Unless they’re Nisi.” (ok, we added that last bit!)
Joking aside, it simply does not makes sense to buy the best lens you can, an item painstakingly engineered for precision and clarity, and then put a substandard filter on the front of it. If you invested in a high-end audio system for it’s impeccable sound reproduction, what speakers would you put on it? Reasonable ones with a well-known name and a “reassuringly expensive” price tag? Or would you choose speakers, designed in every possible way, to compliment the system to which they are attached?
NiSi filters are produced using the best quality, lens grade optical glass. The glass we use is actually superior, in terms of transmittance (the quality and volume of light and detail they let through) than the majority of lenses on the market today. Even when tested on the best lenses available, there is no loss of sharpness.
The improvement in transmittance between the glass exclusively used by NiSi and B270 optical glass is greater than the improvement of B270 over resin!
For example, at the wavelength of 500 nm (red) the transmittance of the resin is approximately 86%, B270 is approximately 92% and NiSi glass is close to 99.9%!
To put it another way; if you stack 3 traditional optical glass filters, losing 8% of the detail each time, cumulatively, only 78% of the detail reaches the lens. With NiSi, it’s 99.7%!! And this is only one aspect, for example the curve of the NiSi glass is much more uniform and there are no secondary effects such as variations in the focus plane or other undesirable effects. For more information on NiSi glass you can learn more here.
Treatments and Multi Coating
The best glass in the world is certainly a fantastic foundation for a photo filter, but is it enough? Are there other key features? According to NiSi yes, and they are categorised as “treatments and multi coatings”.
A series of treatments, applied one over the other, are defined as “Multi-Coating” or MC. Many of these treatments are NiSi proprietary treatments, technology that has been developed or improved internally, especially with regard to IR and Nano® treatments.
- The infrared (IR) treatment is fundamental for chromatic correspondence, as it absorbs and blocks the infrared light. IR is invisible to the human eye but not to the camera sensor which, especially on long exposures, can cause a strong pink/magenta cast. For this reason, the presence of an IR treatment is essential. Furthermore, our filters absorb UV light as well as IR, ensuring excellent uniformity of colours and light/shadow without colour cast.
- Nano® coating is essential to make NiSi filters resistant to the most difficult weather conditions that you are likely to encounter. Water or oil (such as that naturally present on human skin) is certainly not a problem, the filter is cleaned quickly and effectively. Thanks to the Nano® treatment, the water is not spread on the surface of the filter, but remains compact and easy to remove. The Nano® treatment makes NiSi filters weather-resistant and ready for any situation.
- Anti-Reflection: the explanation is in the name, it is used to minimise reflections and therefore the possibility of creating flare or annoying reflected lights. All NiSi filters have some of the lowest reflections in the world.
See the Nano® Coating NiSi® at work here:
Learn more about the chromatic correspondence and neutrality of NiSi filters in this article.
Why is the corner of NiSi filters untreated?
One question we are frequently asked is about the untreated corner of NiSi filters and to a lesser extent the rounded corners – we have heard many different theories. So let’s clear things up with the unfiltered answer:
- The rounded corner serves a couple of purposes (aside from looking good.) Firstly, the rounded edge is more comfortable to hold than a sharp glass corner and is less likely to snag when you are taking it out of the pouch or catch on/scratch/damage other expensive items in your bag. Secondly, the rounded corners are much less likely to break and are tougher in the event of the filter banging into something else. Even the act of placing the filter down on a hard surface could cause the corner to break off, damaging the structural integrity of the glass.
- The mysterious untreated corner. Sometimes the simplest answers are the truth – that is the point at which the robots in our manufacturing stages grip the filter. A clear untreated area provides a safe place to handle the filter without damaging the various treatments as they cure. And because it is such a small area it will never come into the field of view of your lens. There is an additional “peace of mind” benefit to this little area though, it gives you a point of comparison between the treated and untreated areas of the glass so you can see exactly what has been done and that you are holding a genuine, multicoated filter and not just a piece of coloured glass.
Why are there purple/pink reflections?
NiSi filters have the best light transmission curve in the world, allowing a uniform passage of all light frequencies, therefore avoiding chromatic aberrations and colour cast. When we look at them from certain angles there are clear purple/magenta reflections. This effect is due to the IR surface treatment, combined with the particular reflections of the Nano® Coating. In fact, the treatment against infrared light (IR) is purplish to the eye, but it is essential to avoid any magenta cast in the final shot.